Arterial endothelia cells in vivo are continuously subjected to varying degrees of shear strees. These forces have direct effects on the morphology and physiology of the cells and have been implicated as an important factor in atherogenesis. We are designing a simple system for studying the relationship between shear forces and endothelial cell alteration. The system consists of a parallel plate flow chamber which accomodates Thermanox circular cover slips upon which bovine or human umbilical cord endothelial cells are cultured. The flow patterns and shear within the chamber are being characterized using electrochemical shear measurements, flow visualization techniques, and laser doppler anemometry. The design permits studies at shear stresses up to 30 dynes/centimeter squared for periods up to 2 weeks. The cell morphology and ultrastructure are being studied by SEM and TEM. The system is versatile and provides the means for biochemical assays, pulsatile flow, and time lapse photography.